Vibration device enclosed in the core of molds for casting concrete pipes



April 1955 o c. G. LKRKFELDT 3,177,554

VIBRATION DEVICE ENCLOSED IN THE CORE OF MOLDS FOR CASTING CONCRETE PIPES Filed June 10, 1963 2 Sheets-Sheet l April 1965 c. G. LARKFELDT 3,177,554

VIBRATION DEVIOE ENCLOSED IN THE CORE OF MOLDS FOR CASTING CONCRETE PIPES Filed June 10, 1965 2 Sheets-Sheet 2 United States Patent 3,177,554 VIBRATION DEVICE ENCLQSED IN THE (IGRE 0F MOLDS FOR CASTING CONCRETE PiPES ()we Carl Gunnar Liirkfeldt, Stockholm, Sweden, assignor to Ab Skanska Cementgjuteriet, Stockholm, Sweden, a corporation of Sweden Filed June 10, 1963, Ser. No. 286,571 Claims priority, application Sweden, June 25, 1962,

7,051/62 3 Claims. (Cl. 25-127) This invention relates to a vibration device enclosed in the core of molds for casting concrete pipes especially reinforced concrete pipes. In known devices in which the vibrator is enclosed in the mold core the vibrator consists of a unitary eccentric element having eccentric masses secured to a rotary shaft. The conventional casting operation combined with vibration has been found to be involved with certain inconveniences which in the casting operation of reinforced concrete pipes manifest themselves in the form of circumferential displacement of the reinforcing members, which is especially disadvantageous if lying reinforcing members are used consisting of oval iron rings the positions of which in the final pipe cannot be ascertained and are of decisive importance to the position in which the pipes are to be deposited in the ground to attain the advantage of the oval reinforcement. Inconveniences are also involved if standing reinforcing irons are used because the irons are likely to tilt during vibration. Upon close consideration it will be evident that said displacements are due to the fact that the concrete during vibration is subjected to a unidirectional rotation of particles resulting in a travel of the concrete mass in a certain direction relative to the direction of rotation of the eccentric masses. Such travel may also be of disadvantage in case of non-reinforced pipes due to the fact that the slightest sloping position of the core in the mold causes the concrete mix to rise on one side of the mold so that the top surface of the concrete will be inclined.

In accordance with the invention the above named inconveniences can be eliminated if the vibration device provided in the core comprises eccentric elements adapted to rotate in opposite directions. Due to this arrangement the unilateral travel of the concrete mass occurring with the use of a single vibration element is avoided so that the reinforcing iron will not be dislocated. However, in case of two vibrator elements rotating in opposite directions at equal speeds another often undesired effect may be induced because of a possible directional movement of the core in a direction at right angles to the position in which the radii of the two eccentric masses are pointing in opposite directions in alignment with each other, resulting in that the concrete in the places extending at right angles to the directional movement will not be considerably compressed.

In order to avoid the last named inconveniences while maintaing the advantage of the opposite rotation of the eccentric elements, a preferred embodiment of the invention is characterized in that the eccentric elements rotating in opposite direction are driven at different speeds, preferably at slightly different speeds. As a result there of the directional movement imparted to the concrete by the two eccentric elements will be displaced around the circumference because of the fact that the positions in which the radii of the two eccentric masses are pointing in exactly opposite directions will be angularly displaced during each revolution in relation to the speed difference between the driving shafts. The smaller the speed difference, the closer are the directional impulses of movement spaced around the circumference, and all parts of the circumference will be subjected to equal compressive actions.

ing eccentric masses.

3,177,55 Patented Apr. 13, 1985 At normal speed of one of the vibrator shafts it is possible, for instance, to have the relative rotation between the shaft and the radii of the eccentric masses to amount to one revolution per second. Usually the duratron of vibration is between 3 to 15 minutes, for instance about 5 minutes, and it will be obvious therefrom that the concrete will be worked very uniformly. The speed difference of the two shafts in consideration should be by preference smaller than 50%, for instance between 0.1% and 20%. By way of example only, the speed ratio may be 50:51.

The shafts of the eccentric elements may be disposed laterally of each other, but from the constructional point of view it is suitable, as shown in the annexed drawing, to provide the eccentric elements rotating in opposite direction on a common axis. It is also to be understood that each eccentric element may be divided into two or more eccentric masses or Weights which may be axially spaced apart in which case weights rotating in one direction may be disposed axially between weights rotating in the opposite direction, and it will also be understood that there may be provided eccentric Weights rotating at different speeds in the same direction always in combination with weights rotating in the oppositedirection. The masses rotating in different directions should be of equal magnitudes.

The invention is described more closely hereinbelow with reference to the annexed drawing illustrating an embodiment thereof.

FIG. 1 is a vertical sectional view of a mold provided with a device in accordance with the invention. FIG. 2 is an enlarged axial sectional sectional view of an emllgliglrrient of one of the eccentric elements illustrated in In FIG. 1 numeral 1 denotes the external wall of the mold and numeral 2 denotes a tubular mold core. These parts are supported by a table 3 with the intermediary of elastic members, such as rubber blocks 4. The external wall can be removed either by being longitudinally divided or by vertical displacement relative to the core. The fnished pipe rests on a bottom ring 5 which in the embodiment illustrated is suspended from the tubular core 2 and displaceable along the core. In the embodiment illustrated the vibration device is housed in a separate tube 6 which by means of transverse walls 7 is connected to the wall of the core. The vibration device is driven by an electric motor 8 disposed at the lower part of the core.

In the embodiment illustrated two eccentric elements rotating in opposite directions are provided on a common axis. One of the eccentric elements is divided into two groups or parts each having an eccentric mass or masses, one part A being located at the upper end of the core and the other part A being located at the lower part of the core. Between these parts of the element there is provided a second eccentric element B rotating in a direction opposite to the direction of rotation of the element A, A.

The motor 8 carried by the table 3 has a central shaft 9 which in the embodiment illustrated directly drives the eccentric element A, A. The shaft is divided into a plurality of lengths interconnected by elastic clutches 10 and mounted in the bearing boxes 11, 11' and 12 associated with the eccentric elements. By means of rings 13 the bearing boxes are connected to the tube 6. The shaft part mounted in the bearing box 11 carries eccentric weights l4, and the shaft part mounted in the bearing box 11' carries eccentric weights 14. The shaft parts are considered to be supporting shafts for the appertain- In order to rotate the eccentric masses appertaining to the eccentric element B in a direction opposite to the direction on a journal 22 mounted in the box 12 is a sprocket Wheel 19 to which movement is imparted from the sprocket wheel 18 by means of a chain. 'N'on-rotatably connected with the sprocketvwheeli 19 'is a gear vwheel 20 in mesh with a gear wheel 21- which is rigidly secured: to the tubular shaft 15 that carries the eccentric weights 16. Consequently, the last named shaft is-driven ina direction opposite to the direction of rotation of the shaft 9. By suitable choice of the gear. ratio of the gear wheels 20, 21 or sprocket wheels '18, 19 the desired speed difference between'the shafts 9 and 15 can be obtained. Instead of the chain1transmission between, the

sprockets 18, 19, gear wheels maybe used in which case a reversing wheel ,is provided in the transmission to re-" 4 2 679 384 30 I J v verse the direction of rotation ofthe driven shaft;

- The arrangementillustrated by way ofexample in FIGS. 1 and 2 may be modified within Widelimits of the scope of the invention. The number of groupsof eccentric masses A A, B, the mutual positions thereof in the core, and the driving device'rnay be modified which of rotation of theseccentric masses appertaining to the eccentric element A, A v the first" named masses are mounted on a tubular shaft which surrounds the driving shaft 9' and between the" drivingand the driven'shaft'ther'e is provided a trans- An exas mentioned above may compriseshafts located side by side and having individual drive motors or 'a common drive motor.

What is claimed'is: Y g 1; 'In a mold for casting concrete pipes, a mold core, a vibration 'devicehoused in'said core and comprising first and second rotatable eccentric elements, saidfirst eccentric element comprising eccentric masses provided 'one at eitherend of and out of contactfwith said core,

, a first's'haft carrying 1said masses, a tubular shaft surrounding said first shaft; and .said' second eccentric element comprising an eccentric mass' mounted: on said tubular shaft between said 'first namedmasses and out of contact withsaid core and means onone of said shafts V for engaging a driving means 'on'the other of said shafts so that rotation of one of said shafts in one direction will rotate the other shaft in the opposite direction;

2.- A system as set forth in claim 1 wherein said means 1" isa transmissionj gearfor transmitting motion frorn'one' {of said shafts to the other one.

3. A system as defined n claim 2 in which said transfrom 1 m1. V

References Cited by the Examiner 2 UNITED STATES PATENTS" 1,293,662 2/19; -Atterbury Q 2 5-41 2,356,852 8/44 Hutchinson 25-30 1 5/ 54 Livingston e't'al. 25-41 FOREIGN PATENTS 11/58 Canada. 8/60 Canada.

5'ROl3ERT F. Primary Examiner.

mission gear has a transmission ratio slightly differing 

1. IN A MOLD FOR CASTING CONCRETE PIPES, A MOLD CORE, A VIBRATION DEVICE HOUSING IN SAID CORE AND COMPRISING FIRST AND SECOND ROTATABLE ECCENTRIC ELEMENTS, SAID FIRST ECCENTRIC ELEMENT COMPRISING ECCENTRIC MASSES PROVIDED ONE AT EITHER END OF AND OUT OF CONTACT WITH SAID CORE, A FIRST SHAFT CARRYING SAID MASSES, A TUBULAR SHAFT SURROUNDING SAID FIRST SHAFT, AND SAID SECOND ECCENTRIC ELEMENT COMPRISING AN ECCENTRIC MASS MOUNTED ON SAID TUBULAR SHAFT BETWEEN SAID FIRST NAMED MASSES AND OUT OF CONTACT WITH SAID CORE AND MEANS ON ONE OF SAID SHAFTS FOR ENGAGING A DRIVING MEANS ON THE OTHER OF SAID SHAFTS 